1. Technical Field
The present invention relates generally to the field of motors, and in particular to bearings used to mount a rotor shaft to a motor housing.
2. Background Art
One failure mode of prior art rotor bearing assemblies is known as "wallowing," which occurs when the outer ball bearing race of the lead end bearing assembly creeps and spins radially within the bearing cavity in the bracket housing. In one prior art assembly, the bearing and housing are equipped with additional mounting hardware to prevent creepage of the inner and outer races. First, a ball is welded to both the outer and inner races prior to installation, both on the same face of the bearing. The bearing is then assembled in the bracket cavity, without the rotor. The face of the bearing is recessed below the surface of the mouth of the bearing cavity; the balls protrude above the mouth. A tab is then installed, via a self-tapping screw, to the bracket housing adjacent to the mouth of the bearing cavity such that the tab overhangs the outer race. The interference between the tab and the ball on the outer race eliminates outer race rotation. Next, an upset, or burr, is generated on the rotor shaft bearing shoulder/seat. At final motor assembly, the bearing bracket assembly is slip-fitted onto the bearing journal. The upset generated on the shaft bearing shoulder provides a stop for the ball welded to the inner race, prohibiting inner race rotation.
This prior art bearing assembly is disadvantageous because the bearing assembly must be seated in its receiving cavity before the tab affixed to the bracket housing can be attached and before the bearing bracket assembly is slip-fitted onto the bearing journal. These steps require additional time and labor, resulting in increased manufacturing costs.
There is thus a need for a rotor assembly in which the problem of wallowing is addressed without requiring the mounting of additional hardware after the bearing assembly is seated in its receiving cavity.